Professor Kim Gun-tae of UNIST Department of Energy and Chemical Engineering succeeded in mass production of green hydrogen (H2), which is close to 100% purity, by decomposing liquid ammonia (NH)) into electricity. According to the analysis technology proposed by the researchers, this method consumed three times less power than hydrogen by electrolysis.
Ammonia synthesis is the most efficient method of transporting hydrogen. If ammonia is synthesized with hydrogen, it can carry 1.5 times more hydrogen and has less loss during transportation. Another advantage is that it can utilize current liquid ammonia transportation infrastructure. However, while the technology for synthesizing hydrogen into ammonia has been commercialized, the technology for rehydrogenation in ammonia is still in its early stages.
The research team succeeded in extracting hydrogen from liquid ammonia using porous Nifoam electrodes. Nickel foam electrode surface has catalytic (platinum) particles evenly applied through cyclic voltammetry, which is highly efficient. If the synthesized electrode is put in liquid ammonia and an electric current is flowed, liquid ammonia can be decomposed (electrolyzed) and hydrogen can be obtained. The Faraday efficiency, an indicator of hydrogen purity, was over 90%, and the current density of the chemical reaction rate was over 500 mA cm-2.
In addition, a new protocol that quantitatively analyzes the amount of gas generated in real time using gas chromatography (gas analyzer) was proposed to find efficient ammonia electrolytic process conditions (acidity of electrolytes, etc.).
An optimized driving environment can produce 569 liters of hydrogen at 1 kWh of power. Compared to electrolysis of water, electricity consumption is three times lower. This demonstrates that ammonia can produce green hydrogen at less power and cost than electrolysis.
“We used electrode fabrication method that has excellent hydrogen production activity in ammonia electrolytic environments,” the research team said. “We expect this electrode to contribute greatly to simplifying ammonia electrolytic system and reducing construction costs.” If the high-efficiency electrodes presented in this study are applied to the ammonia electrolytic process, commercialization of ammonia electrolytic hydrogen production technology will be faster. The study also proposed a variety of research possibilities to re-resource ammonia, and even waste ammonia, into “CO2-free hydrogen,” pioneering a new paradigm for renewable energy.